how much valve spring for stock components?

[athomp]

How much valve spring should stock rockers, studs and push rods be able to handle? I have a stock 350 in a ashphalt circle track car. A couple of years ago I lost an engine to a broken valve so in my current engine I put in a bit better valve springs - 358 lbs/inch, 115-120 on the seat. Otherwise pretty much stock - stamped 1.5:1 rockers, stock pushrods, screw-in 3/8" rocker studs, .390/.410 lift cam. Maximum 5800 rpm. The problem is that I keep breaking rocker arms, pushrods and rocker studs. Too much spring? What spring would be recommended for this engine?
Thanks

[ZIGGY]

Sounds a little stiff. Hyd. cam? What does the cam maker call for? Who made the screw-in 3/8 studs;do they have a shoulder? I'm having trouble seeing those springs break a quality 3/8 stud on their own.

[donc]

If thats an "extra area cam" whats the duration #s @ .050?

[Alan Roehrich]

I can tell you that 260 pounds of open pressure will not break good quality studs, rockers, and pushrods. You have another very serious problem. Or you're using cheap parts.

We've run right at 400 pounds open on stock rockers.

[Keith Morganstein]

I can tell you that 260 pounds of open pressure will not break good quality studs, rockers, and pushrods. You have another very serious problem. Or you're using cheap parts.

We've run right at 400 pounds open on stock rockers.

Yea, something seems wrong.

The OP needs to share more details about the parts he is using.

ARP studs, Elgin racing stamped rockers, trend pushrods should not be breaking.

If those good parts are being used something is wrong with the... set-up. geometry, binding against the stud, rocker or spring coils. Or the spring is much stronger than stated.

[metriccar]

I've run Isky 8205 springs which are 440 lbs/in. and 160 lbs seat pressure on a .53 lift solid flat tappet cam with cheap stock replacement rockers with no problems. I upgraded the pushrods to avoid flex and had 3/8" screw in studs and guideplates, stainless steel valves. I ran this for a season but since went to a milder cam/springs.

The stamped rocker arms can take a lot of abuse but I'd make sure you are getting the ones with the grooves in the balls for better cooling. 260 pounds on the nose is not a lot at all, especially for screw in studs. And .43 lift cam is not that high. If it were higher I'd think the valves were hitting the piston but I'd still want to ask, has this cam been degreed with a wheel when installed? I'd say valve to piston issues could be a culprit but seems like you'd have a lot of leeway with that low lift of a cam.

Is the .390/.410 lift after the 1.5 rocker ratio or the actual lift of the cam itself? I'm guessing after the 1.5 rocker ratio.

Yeah there are a few things you could do real easy, like check how much groove you still have left on the rocker arm / stud groove at full lift but .41 lift should not be a problem.

[Baprace]

I would install a .060 shim under the valve springs to increase the pressure or -.050 valve locks, you are too soft for 5800 rpm's. You only have 260 lbs. of open pressure. or bring the rpm's down to 5200/ 5300 and that should help the problem with that spring pressure.

Second issue may be the oil pan, you need one with a kick out and the pump pickup should be on the right side of the pan if you are on a flat track/semi flat track, it's possible you are out of oil in the corner, the lifters pump down and the valves start clattering, that will break stock rockers also.

[ZIGGY]

I thought the man indicated he had 358 on the nose, which Alan intended to round to 360 in his post but typo'd as 260. (??)

[Alan Roehrich]

I thought the man indicated he had 358 on the nose, which Alan intended to round to 360 in his post but typo'd as 260. (??)

No, he said the rate was 358. With 120 on the seat and .400 lift, that comes out to around 260.


rate x lift = p + seat = open (where P = pressure from lift)

358 x .4 = 143 + 120 = 260 +/-

Yes, I rounded it off some.

[ZIGGY]

Ah, didn't dawn on me. Thank you.

[athomp]

A few more details: It's a hydraulic cam with .390/.410 VALVE lift. 218/224 duration at 0.050 lift. Was intalled starght up but degreed to check. Pushrods are original factory stock. Rockers were original factory stock but I broke 4 last year so I replaced then with Summit rockers SUM-G6800. I haven't broke any of those yet but it's early in the season. Studs are Summit SUM-G1675. Springs are Summit SUM-17400. Oil pan has a kickout and the track is banked 12-15 degrees.

[Baprace]

A few more details: It's a hydraulic cam with .390/.410 VALVE lift. 218/224 duration at 0.050 lift. Was intalled starght up but degreed to check. Pushrods are original factory stock. Rockers were original factory stock but I broke 4 last year so I replaced then with Summit rockers SUM-G6800. I haven't broke any of those yet but it's early in the season. Studs are Summit SUM-G1675. Springs are Summit SUM-17400. Oil pan has a kickout and the track is banked 12-15 degrees.

I stand by my original assessment, not enough valve spring pressure for your rpm's, especialy with 218/224 @ .050 , those little lobes are pointed, Second item is your pushrods, not strong enough, if you have to use stock pushrods start hunting around for the old GM blue stripes, they were used in the late 60's and 70's on high performance engines, if you look at one very closely you will see one end has a hardened tip which goes against the rocker, if not put in a set .080 wall aftermarket pushrods and step up the spring pressure.

[jeff swisher]

I would think it was an oil related issue or spring pressures. Like was stated.
I have and still run stock gm rockers and stock gm pushrods with many of my builds and never broke any.
But these are not circle track engines..Drag race and daily driver stuff..I set most up at 110 seat and 325-335 over the nose on most of them. I try to stay under 345 open..these are old comp magnum grinds and twisted to 7500rpm on the 292H and 7200rpm on the 280H..
I would say you have other issues..most of my parts are from the mid 70's

[athomp]

I don't think it's an oiling problem - getting good pressure (60-80psi on the track)and there's no sign of galling or discoloration from heat on the balls or rockers.
As for binding - I can still feel some groove on the rocker when the valves are open.

I can try the shims and better pushrods but (and this is probably a stupid question) how does the springs being too weak cause the parts to break?

Thanks

[af2]

5800 rpm??? And you are breaking valve train?

Run a stock spring at 80 seat and 160 over and the problem will go away.